My "understanding" is you can use the same practice as beer. So for example 5oz for a 5 gallon batch. I personally use corn sugar. I will state, I have NOT bottled my first batch yet, this is just based on videos i have watched.

I couldn't get a straight answer out of anyone as well. What i did was move the cider into a bottling bucket and added one can of apple concentrate and then bottled. I put cider into 3-20 ounce bottles to check for carb leveling and started opening bottles every other day after they began to harden. ( after 3 days) The bottles were sitting at about 65 degrees during this time. The cider was at .998 before I moved it into the bottling bucket. It took me 8 days to reach my desired carb level.

I hope this helps...knowing what i know now i would have added splenda to the cider to get my desired sweetness as well as the concentrate. My understanding is that splenda is a non-fermentable suger and u wouldn't lose the sweetness during the carb process.

I have heard 1/8 cup to 1/4 cup per gallon (depending on how carbonated you want), but that is not backed up by my personal experience. I will backsweeten my first non-still batch of cider in about 3 weeks, and I'll let you know how that turns out. Dextrose is supposedly preferable because of the "fizzy" quality of the bubbles, but any fermentable sugar should work.

As far as non-fermentable sugars go, I would recommend using Xylitol, a natural alcohol sugar. (Stevia also works, though it has its own flavor, which I personally like but you may not want in your brew). Splenda is sucralose-- nasty stuff. A solution of sucralose will eat through an aluminum pan; not what I want in my brew. Go with Xylitol instead.

I couldn't get a straight answer out of anyone as well. What i did was move the cider into a bottling bucket and added one can of apple concentrate and then bottled. I put cider into 3-20 ounce bottles to check for carb leveling and started opening bottles every other day after they began to harden. ( after 3 days) The bottles were sitting at about 65 degrees during this time. The cider was at .998 before I moved it into the bottling bucket. It took me 8 days to reach my desired carb level.

I hope this helps...knowing what i know now i would have added splenda to the cider to get my desired sweetness as well as the concentrate. My understanding is that splenda is a non-fermentable suger and u wouldn't lose the sweetness during the carb process.

How much cider were you making. I'm making a 6 gallon batch and I'm wondering how many cans of concentrate to use.

I have used simple syrup with success, but because there are too many variables to deal with, I recommend using your hydrometer. Typically you should raise the sugar content up .003 above your desired sweetness.
I will also suggest bottling one cider in a plastic bottle (like a soda bottle) so you don't have to open a bottle every other day to insure proper carbonation -you can tell it's done when the bottle tightens up.

It allows you to enter the style...gallons in batch and temperature of your batch at bottling...then it will recommend types of fermentables and weights for each. It's not exact, but it gives you a good reference.

I personally prefer Corn Sugar/Dextrose for bottling because it won't impart any flavors in your cider (not that you use a whole lot)

I like mine closer to beer or soda and fritzy instead of like champagne. So I use 3.9 oz of corn sugar per 5 gallons. Some people will go up to 1 oz per gallon.

I wonder how much of the CO2 remaining is affected by secondary racking? For example if I do a Oatmeal Stout, letting it sit in the fermenter for 12 days, then bottle, vs letting it sit in the fermenter for 12 days, racking it into a carboy for 2 weeks, and then bottling it?